A chemically amplified resist has been an essential material technically common in lithography using light or charged particle beam such as electron beam or ion beam. However, such a resist is susceptible to use environment and is known as a resist hard to handle.
In a case where a chemically amplified resist is coated with a water-soluble coating material, there is a problem that acid generated through exposure to light is neutralized by the coating material or that even without exposure to light, acid components contained in the coating material erode a surface layer of the resist, which generates the same state as in the case conducting exposure to light. Thus, even a trace amount of acid present in coating material considerably affects sensitivity of resist. This phenomenon comes out as film-thinning in case of a positive-type resist and as formation of a layer having low-solubility or insolubilized layer in case of a negative-type resist.
As methods for preventing these phenomenons, a method where pH decrease is controlled by using a buffer solution containing a weak acid and an amine (JP-A-H11-189746) as an aqueous solution of coating material, a method using a composition containing a fluorinated aliphatic sulfonic acid or a fluorinated aliphatic carboxylic acid (JP-A-2003-29410) and the like as an aqueous solution of coating material have been proposed.
Moreover, there is a problem that, since the surface is hydrophobic after film formation of a chemically amplified film, it is difficult to coat the surface with an antistatic agent, without imparting surface activity to the surface through addition of surfactant or the like. In an antistatic film, which is used to coat a resist, evenness and uniformity are required. For the purpose of improving coatability of antistatic agent, it has been conventionally proposed to allow the agent to contain surfactant or polymer serving as binder. For example, JP 06-3813 A reports on an electroconductive composition for pattern forming, comprising sulfonated polyaniline-containing composition which consists of a solvent-soluble polymer compound and/or surfactant as components. This document describes that uniformity, coatability, conductivity and the like can be enhanced by the technique. However, use of surfactant for imparting coatability adversely affects properties of resist by formation of a mixing layer or the like. In this regard, it has been proposed that by use a polymer compound having a nitrogen-containing functional group and a hydrophobic group at a terminal as antistatic agent for a chemically amplified resist, influence on chemically amplified resist can be reduced (JP-A-2002-226721). Moreover, JP-A-8-109351 teaches that a water-soluble polymer or a polymer compound forming emulsion in an aqueous system can be used as binder polymer in a composition having an effect of preventing charge-up.
An antistatic agent for resist is used for imparting temporary conductivity in the time of processing a resist and therefore, it is required that the agent not be insolubilized so that the agent may be easily removed with water or alkali water. Among water-soluble polymers, some of those having an ester group, which generate acid through hydrolysis and the like to thereby affect resist, are not suitable. Also, those having a crosslinkable terminal may be insolubilized during the processing and then cannot be removed. Further, water-soluble polymer having basicity, which causes precipitation when used in combination with a water-soluble electroconductive polymer having a sulfonic acid group, is not preferred.
Recent progress on semiconductor devices is remarkable. With improvement in precision of resist processing, demands for evenness and uniformity in antistatic agent film and for higher resolution of resist are more and more increasing. In conventional techniques, coatability of antistatic agent is insufficient and furthermore, influence on resist shape caused by additives such as surfactant contained in conventional antistatic agents determines quality of semiconductor products. That is, in microfabrication process of resist of 100 nm or less, resist shape is controlled on the order of several nm. In such a microfabrication process, even a slight influence on resist caused by antistatic agent may significantly impair rectangleness of resist. Further, resist having been patterned through developing process is subsequently subjected to dry etching for pattern transcription onto the substrate. For the purpose of preventing collapse of resist patterned according to miniaturization of the minimum circuit line width in semiconductor devices, resist films are being more and more thinned so that an aspect ratio may be appropriate for resist pattern. Changes in resist shape have a great influence on pattern transcription at the time of dry etching process. In other words, with advance on technology for producing semiconductor devices, there are increased demands for antistatic agent which can maintain performance of chemically amplified resist and antistatic agent which can further reduce influence on resist is desired. Furthermore, in case of non-chemically-amplified resist, inorganic resist is sometimes employed in ultra-microfabrication process on the order of 10 nm, which may cause film thinning.